Levodopa

Pharmacology

Crosses the blood-brain barrier and is converted to dopamine in basal ganglia and periphery.

Pharmacokinetics

Absorption

Absorbed from the small bowel. T max is 0.5 to 2 h and may be delayed in presence of food. Rate of absorption is dependent upon rate of gastric emptying, pH of gastric juice, and length of time drug is exposed.

Distribution

Does not cross the blood-brain barrier.

Metabolism

Metabolites are dopamine and homovanillic acid (HVA). Extensively metabolized (greater than 95%) in the periphery and by the liver.

Elimination

Plasma t ½ is 1 to 3 h. Excreted primarily in the urine; 13% to 42% of HVA excreted in the urine within 24 h.